Advancement device for a horizontal earth boring machine

ABSTRACT

A system for advancing and retracting rail mounted horizontal earth boring machinery. The system includes a walking beam structure slidably mounted to the chassis of the horizontal earth boring machinery. The walking beam is located underneath the horizontal earth boring machinery between the rails. The walking beam has pins which can be engaged with the rails supporting the horizontal earth boring machinery. The pins are actuated by a pivotally mounted rod which slidably engages a pin actuating linkage located on the walking beam. By slidably mounting the walking beam under the horizontal earth boring machinery and by controlling the engaging and disengaging of the pins associated with the walking beam by the slidably engaged rod, simple and inexpensive mechanical control of the earth boring machinery can be accomplished at a specific control position on the unit. Further, the overall length of the horizontal earth boring machinery is reduced by the placement of the walking beam under the chassis of the horizontal earth boring unit.

United States Patent [191 Linsay Apr. 30, 1974 1 1 ADVANCEMENT DEVICEFOR A HORIZONTAL EARTH BORING MACHINE [75] Inventor: Michael Linsay,South Euclid, Ohio [73] Assignee: Allied Steel & Tractor Products,

' Incorporated, Cleveland, Ohio 22] Filed: Feb. 20, 1973 21 Appl. No.:325,884

[52] US. Cl 173/152, 175/62, 254/29 [51] Int. Cl. E2lc 5/11 [58] Fieldof Search 173/152, 156; 175/62, 122;

Primary ExaminerErnest R. Purser Attorney, Agent, or FirmLyon & Lyon [57 ABSTRACT A system for advancing and retracting rail mounted 4horizontal earth boring machinery. The system includes a walking beamstructure slidably mounted to the chassis of the horizontal earth boringmachinery. The Walking beam is located underneath the horizontal earthboring machinery between the rails. The walking beam has pins which canbe engaged with the rails supporting the horizontal earth boringmachinery. The pins are actuated by a pivotally mounted rod whichslidably engages a pin actuating linkage located on the walking beam. Byslidably mounting the walking beam under the horizontal earth boringmachinery and by controlling the engaging and disengaging of the pinsassociated with the walking beam by the slidably engaged rod, simple andinexpensive mechanical control of the earth boring machinery can beaccomplished at a specific control position on the unit. Further, theoverall length of the horizontal earth boring machinery is reduced bythe placement of the walking beam under the chassis of the horizontalearth boring unit.

9 Claims, 5 Drawing Figures PATENTEUAPRBO 191 3807509 SHEET 1 BF 2 i ZAz' 54 30/04 i! 73% This invention relates to horizontal earth boringmachinery. More specifically, this invention is directed to improvedmeans for controlling and mounting a walking beam for horizontal earthboring machinery.

Heavy-duty earth boring equipment has been developed for boringhorizontal holes under a variety of barriers, such as roadways, where itis inconvenient or impossible to dig a trench traversing the barrier.Such equipment generally includes a rail mounted frame to which a powerunit, a drive train and an auger are attached. A cylindrical casingpusher is often included near the back of the auger to force casing intothe bore as the auger advances. The larger of these devices have alsoemployed powered means for advancing and retracting the horizontal earthboring machinery along the rails during the operation of the unit.Walking beams have been employed in combination with rails to which thebeams may be selectively engaged and disengaged. The walking beams actto anchor a hydraulic cylinder or other such power means which acts'fromthe anchoring point of the walking beam to push or pull the horizontalearth boring unit along the rails. The walking process is accomplishedby first engaging the walking beam with the rails. A horizontal earthboring unit is then forced to advance by actuating a hydraulic cylinderanchored through the walking beam. After the horizontal earth boringunit has'advanced a predetermined distance, the walking beam isdisengaged from the rails and brought forward to a next engagement withthe rails. The process may then be repeated to create a walking typeaction to either advance or retract the boring unit.

The walking beam unit has generally been placed behind the horizontalearth boring machinery in the 'power driven units. A problem associatedwith the 'the dismounting of a single operator from the central controlposition to actuate the walking beam as the system is advanced orretracted. To avoid the requirement for either two operators or oneoperator controllng the equipment at a plurality of positions,hydralically operated control systems have been devised. These controlsystems have not met with resounding acceptance because of the addedcomplexity of the machinery and the cost of incorporating such systemson the unit.

A second problem associated with the placement of the walking beambehind the earth boring unit is the resulting overall length of theunit. In operating boring machinery, it is necessary in many instancesto dig a pit into which the machinery must be lowered to reach theelevation of the intended horizontal bore. This pit is often for thesingular purpose of positioning the horizontal earth boring equipmentand the cost of excavating such a pit must be considered as being partof the boring cost. As a result of this added cost, it is beneficial tomake the earth boring units as'compact as possible. By extending thewalking beamv out behind the unit, a larger pit is required. Also, whenthe operator is required to go back to the walking beam to actuate thelocking mechanism, an even larger pit is necessary.

A compact power advancement system for horizontal earth boring machineryrequiring a single operator who can, act to control the unit 'fromasingle station has been sought. Such a unit would most advantageouslyincorporate simple mechanical linkages for operating system for ahorizontal earth boring unit which is com' pact, requires a singleoperator to operate the unit from one control position and incorporatessimple, inexpensive mechanical control linkages. The walking beam of thepresent invention is positioned beneath, rather than behind, thehorizontal earth boring unit chassis. By positioning the walking beambeneath the horizontal earth boring unit, the overall size of the unitis not influenced by the power advancement means whatsoever. Further,the central placement. of the walking beam makes it possible for asingle operator to manipulate the locking mechanis m of thewalking beamfrom a central control station throughmechanical linkages.

A second object of the present invention is to provide a walking beamwhich is slidably mounted to the chassis of the horizontal earth boringunit. By slidably mounting the walking'beam tothejchassis rather thandirectly to the rails, the walking beam' will not interfere with theadvantageous placement of the various components of the horizontal earthboring unit which would be necessary to avoid the path taken by thewalking beam as it oscillates relative to theearth boring unit duringthe walking process. This central placement of the walking beam on. thechassis has most advantageously affected the overall size and complexityof the unit.

Another object of the present invention is to provide mechanical linkagebetweenthe operator control station of the unit and the lockingmechanisms of the centrally located walking beam. A .pivotally mountedrod is provided on the horizontal earth boring unit which slidablyengages the locking mechanism of the walking beam. Because ofthis'sliding engagement,- the control linkage remains relativelyuncomplicated and .at'the same time provides positive control as thewalking mechanism oscillateswith respect to the control posi-- tion ofthe earth boring unit.

Thus, a power advancement system fora horizontal earth boring unit isdisclosed which reduces the size of the overall unit, allows asingleoperator to control the entire operation from a central control positionand incorporates simple, inexpensive mechanical control linkages tooperate the power advancement system. Further objects and advantageswill become apparent from the discription herein.

FIG. 1 is a side view of the horizontal earth boring unit specificallyillustrating the central control station.

FIG. 2 is a cross-sectional view taken alongline 2 2 of FIG. 1 whichillustrates the locking mechanism in the locked position. a

FIG. 3 is a fragmentary cross-sectional view taken along line 2-2 ofFIG. 1 illustrating the locking mechanism in its unlocked position.

FIG. 4. is a cross-sectional plan view taken along line 4-4 of FIG. 1illustrating the locking mechanism, the locking mechanism controls andthe walking beam.

FIG. 5 is across-sectional view taken along line 5-5 of FIG. 2illustrating the walking beam as it is carried by the carriage of thehorizontal earth boring unit.

Turning now to the drawings, FIG. 1 schematically illustrates thehorizontal earth boring unit as basically comprising a power unit 10, atransmission unit 12, a casing pusher 14 and an auger 16. A chassisgenerally designated 18 provides a mounting base for the horizontalearth boring unit. Two parallel rails 20 having cross ties 22 supportthe chassis 18.

As shown in FIG. 2, the chassis generally designated 18 includes twoangle members 24 and 26 which extend from the back of the unit to thecasing pusher l4 and ride on the bearing surfaces 28 of the rails 20.The chassis members 24 and 26 have plates 30 fixed to the chassismembers 24 and 26 which extend outward in pairs. Pivoted arms 32 arepositioned between the pairs I of plates 30 and are pivotally mountedthereon about pins34. Locking plates 36 are welded to the arms 32 toengage the rails 20 below the bearing surfaces 28. These lockingassemblies are provided to-keep the horizontal earth boring machine onthe rails when in operation.

A walking beam generally designated 38 in. FIGS. 4 and 5 is providedbeneath the chassis 18 for advancing and retracting the horizontal earthboring unit along the rails 20. The walking beam 38 includes a crossmember 40 extending across the width of the walking beam 38 at itsforward end and two skids 42 and 44 abutting the cross member 40 andextending rearward the length of the walking beam 38 forming its lowersurface near the rails 20. Channel members 46 and 48 which run thelength of the walking beam 38 form the sides of the walking beam 38. Thechannel members 46 and 48 are welded to the cross member 40 and theskids 42 and 44 to form a single walking beam structure. A mountingplate 50 is positioned across the back of the unit between the channels46 and 48. A supplemental brace 52 is attached to the cross member 40 ofthe walking beam 38. The supplemental brace 52 includes plates 54 and 56which extend rearward to the mounting plate 50. The supplemental brace52 acts to support the mounting'plate 50 atits center to reduce theeffect of bending moments on the mounting plate 50 which is otherwiseonly attached at its ends to the channelrnernbe'rs 46 and 48. Spacers 58and 60 are positioned on top of the channel members 46 and 48respectively.

Means are provided for selectively engaging the walking beam with therails 20. Selective engagement may be provided by pins 62 and 64slidably mounted to the walking beam 38. The pins 62 and 64 are toextend laterally on the walking bean 38 into selective engagement withslots 66 provided through the rails 20 for this purpose. Reinforcingmembers 68 are provided at each slot 66 to prevent tearing of the railsunder the high loads imposed during operation of the walking beam 38.The slots 66 are spaced periodically along the rails 20 to accommodatethe advancing or retracting walking beam 38 as it first engages and thendisengages therails in successive steps to advance the horizontal earthboring unit. The spacing of the slots 66 is deter- The pins 62 and 64are slidably mounted in foursided guide structures which guide the pins62 and 64 laterally into and out of engagement with the rails 20. Aguide structure is provided for each pin. The guide structures extendourward to the channel members 46 and 48 where pin holes 70 and 72accommodate the pins 62 and 64 as they extend outward to engage theslots 66. The forward side of each guide structure is formed by the backside of the mounting plate 50 which extends across the width of thewalking beam 38. Horizontal top plates 74 and 76 are positioned directlyabove the pins 62 and 64 respectively and are welded to the mountingplate 50. Horizontal bottom plates 78 and 80 are similarly attached tothe mounting plate 50 and extend below pins 62 and 64. The horizontalplates 74 through 80 are slightly wider than the width of the pins 62and 64 to allow unrestricted passage of the pins 62 and 64 between thehorizontal plates. Back plates 82 and 84 are welded to the respectivehorizontal top and bottom plates in positions parallel to the mountingplate 50 and spaced therefrom by the width of the horizontal plates. Thepins 62 and 64 may be of any convenient cross-section. A preferreddesign to minimize wear and provide good shear strength includes asquare cross-section which is reduced at its leading end to facilitatethe insertion of the pin through the slots 66. The pins 62 and 64 are ofsufficient length to prevent binding within the four-sided guidestructures. The pin length must be compromised to allow adequate spacefor the pin actuating means which is to be located between the pins 62and 64. The lengths of the pins must be determined from establishedengineering principles. These lengths are influenced by the width of thewalking beam 38, the design of the actuating mechanism for locking thewalking beam 38, and the mechanical advantage available to move thepins. Also to prevent binding of the pins, due to moment forces exertedthereon, the various plates 74 through 84 should preferably extendinward to points near the furthest retracted positions of the innermostends of the respective pins 62 and 64. However, it is preferred that theplates do not extend so far toward the center of the walking beam thatthey might interfere with the actuating mechanisms associated with thepins 62 and 64.

An actuating means is provided to control the engagement and retractionof the locking pins 62 and 64. In the preferred embodiment, this lockingmeans includes a control rod 86 which is pivotally mounted to thechassis 18 through bearing 88 and to the walking beam 38 on the mountingplate 50 through bearing 90. The bearing 90 mates with the control rod86 in sliding engagement which allows the walking beam 38 to movelongitudinally with respect to the control rod 86. A

pivot arm 92is slidably mounted on the control rod 86 adjacent thebearing 90. The pivot arm 92 is constrained to pivot with the controlrod 86' at any point on the control rod 86 along the length of travel ofthe walking beam 38 with respect to the horizontal earth boring unit.The control rod 86 may be of any cross section which allows the pivotarm 92 to slide thereon I but prevents the pivot arm 92 from rotating onthe'con mined by the operating stroke of the drive mechanisms 7 forcingthe machinery along the rails 20.

trol arm 86. A square rod is employed in the preferred embodiment as thecontrol rod 86. The pivot arm mates with the control rod 86 by means ofa square hole centrally located in the pivot arm 92.. Sufficienttolerance is allowed between the square control rod 86 and the pivot arm92 in order that the pivot arm 92 may freely slide along the control rod86. However, the square hole in the pivot arm 92 should not be so largeas to allow the square control rod 86 to rotate relative to the pivotarm 92.

The pivot arm 92 includes slots 94 and 96 located at either end thereof.Pins 98 and 100 are positioned through the pivot arm 92 and the slots 94and 96 to pivotally mount connecting links 102 and 104. Connecting links102 and 104 are also pivotally mounted at their outward ends by means ofpins 106 and 108 in yoke sections of the locking pins 62 and 64 locatedat the inner ends of the pins 62 and 64. One horizontal upper guideplate 74 extends inward to a point near the center of the walking beam38 to form a mounting base for a stop 110 which is positioned tointerfere with the actuating mechanism of the pins 62 and 64 to preventexcessive retraction thereof. FIGS. 2 and 3 illustrate the pin actuatingmechanism having the pins in the engagement position and in theretracted position respectively. Spring means may be conventionallyprovided to bias the pins 62 and 64 toward the locked position as shownin FIG. 2. If a spring means is employed for so biasing the pins 62 and64, the operator will not be required to operate the actuating means tore-engage the pins as they approach a new slot 66.

To operate the actuating means, an arm 112, as best shown in FIG. 4, isrigidly clamped to the control rod 86. Linkage 114 is pivotally mountedto the arm 112 at a point eccentrically located with respect to thecontrol arm 86. The linkage 114 is pivotally mounted at its upper end tothe walking beam control lever 1 16. Thus, as the walking beam controllever 116 is actuated, the control rod 86 is rotated. As the control rod86 rotates, the locking pins 62 and 64 will engage or disengage from therails 20 by means of the actuating mechanism centered about the controlrod 86 between the pins 62 and 64. By employing the control rod 86, thewalking beam control lever 116 may be centrally located at the controlstation. The control rod 86 extends from a point where the control levercan be conveniently linked thereto through simple and inexpensivemechanical linkage to a point beyond the furthest backward point oftravel of the walking beam 38. The use of this mechanical linkageenables the operator to control the walking beam 38 from the centralcontrol area of the horizontal earth boring machine and further allowsthe positioning of the walking beam underneath the horizontal earthboring unit rather than behind the unit. One purpose for locating thewalking beam behind the unit in the more conventional systems is toallow easy access to the walking beam for mechanical control thereof.The present system is able to advantageously locate the walking beambeneath the unit without complicating the control mechanisms.

Means are provided for mounting thewalking beam 38 to the underside ofthe chassis 18. Such support means must be capable of keeping thewalking beam 38 in alignment with respect to the rails 20 in order thatthe pins 62 and 64 associated with the walking beam 38 will be capableof engaging the rails by lining up with the slots 66. Also, the supportstructure is preferably located under the chassis 18 so as not tointerfere with the travel of the horizontal earth boring unit along therails 20. One device for accomplishing this support function is providedby a support frame generally designated 118. The support frame 118 isfixed to a chassis member 120 by fasteners 122. The support frame 118has a top section 124 which extends to the angle members 124 and 126 ofthe chassis 18. Vertical sections 126 and 128 then extend downwardadjacent rails to a point just below the walking beam 38. Flanges 130and 132 extend inward from the vertical sections 126 and 128 a distancesufficient to support the skids 42 and 44 of the walking beam 38. Thesupport frame 1 18 runs underneath the chassis 18 from the back end ofthe angle members 24 and 26 to the casing pusher 14. The channel members46 and 48 in combination with the skids 43 and 44 and the spacers 58 and60 fit beand bind therein. The channel members 46 and 48 of the walkingbeam 38 are also positioned sufficiently close to the vertical sections126 and 128 of the support frame 118 so that the walking beam 38 cannottwist about a vertical axis and bind under the chassis 18. Slots 134 areprovided along a' substantial portion of the vertical sections 126 and128 of the support frame 118 to allow unobstructed passage of the pins62 and 64 into engagement with the rails 20. Further, the slot 134allows the horizontal earth boring unit to advance while the pins 62 and64 are locked within the slots 66.

By positioning the support frame 1 18 on the carriage 18, the walkingbeam 38 which is supported by the support frame 118 will not interferewith the movement of the horizontal earth boring unit. This is true eventhough the walking beam 38 is centrally mounted under the chassis 18.Conventional systems employ the rails 20 to mount the walking beam 38.Such a system would not be practical in this instancefThe method ofmounting the walking beam 38 in the present invention therefore enablesthe placement of the walking beam 38 under the chassis 18.

To cause the walking beam 38 to move relative to the chassis 18 of thehorizontal earth boring machinery, driving means are provided. Suchmeans must be capable of selectively providing both tensile andcompressive forces in order that the walking beam 38 can be 'moved ineither direction relative to the horizontal earth boring unit. Onedevice for accomplishing this function includes the use of one or morehydraulic cylinders 136 having a first end attached to the walking beam38 and a second'end attachedto the chassis 18 of the horizontal earthboring unit. Two cylinders 136 are provided on the preferred embodiment.The rod ends 138 of the hydraulic cylinders 136 are coupled by means ofpins 140 to bracketts 142 and 144 which are in turn fixed to themounting plate of the walking beam 38. The mounting plate 50 is locatedbetween the bracketts 142 and 144 and the locking pins 62 and 64. Thisallows the force of the cylinders 136 acting through bracketts 142 and144 to pass directly through the locking pins 62 and 64 into the rails20. The cylin-- der ends 146 and 148 of the hydraulic cylinders 136 arelikewise attached by means of pins 150 to bracketts 152 and 154. Thebracketts are in turn mounted on the support member 156 of the chassis18. The cylinders 136 are hydraulically coupled with a pump powered bythe power unit 10. This hydraulic pump is most conveniently a variablevolume pump which has the characteristic of going to zero output whenthe cylinders reach their minimum or maximum extensions. A pump control158 is shown in FIG. 1. Also shown in FIG. 1 is clutch control 160 andthe shift mechanism 162 for thetransmission 12.

Summarizing the operation of the horizontal earth boring machinery withspecific attention paid to the advancement mechanisms, the horizontalearth boring unit is positioned on the tracks 20 and the walking beam 38is locked into the tracks 20 with the cylinders 136 contracted. Thecylinders 136 are then expanded by operating control lever 158 whichactivates the variable volume pump. As the cylinders 136 expand, theypush the earth boring unit forward along the rails 20. When thecylinders have reached a maximum expanded position, the walking beam 38is unlocked from the rails 20 by means of the walking beam control lever116 which pivots the control rod 86 which in turn disengages the pins 62and 64 through the pivot arm 92. When the walking beam 38 is unlocked,the cylinders are caused to contract which pulls the walking beam 38 arethen re-engaged with the rails 20 by repositioning the walking beamcontrol lever 116. The process may thenbe repeated to advance the unitfurther.

Thus, an advancement system is disclosed which provides for a walkingbeam located beneath the chassis of the earth boring'unit. The systemmay be simply and inexpensively controlled through mechanical linkage ata control center conveniently near the transmission, clutch, and pumpcontrols. While embodiments and applications of this invention have beenshown and described, it would be apparent to those skilled in the artthat many more modifications are possible without departing from theinventive concepts herein described. The invention,therefore, is not tobe restricted except as necessary by the prior art and by the spirit ofthe appended claim.

I I claim:

l. A horizontal earth boring device comprising an earth boring unit;

a chassis for mounting said earth boring unit thereto;

a plurality of rails supporting said chassis; a walking beam; drivemeans for driving said walking beam relative to said chassis; lockingmeans operably mounted on said walking beam for selectively engagingsaid rails; actuating means'operably linked to said locking means foractuating said locking means; and I support means fixed to said chassisfor slidably supporting said walking beam. 2. The device of claim 1wherein said walking beam is located under said chassis.

3. The device of claim 1 wherein said support means includes a topsection mounted to said chassis; 7 two mutually parallel, vertical sidesections,'said vertical side sections being spaced to fit about saidwalking beam to keep said walking beam aligned;

and.

two bottom sections extending inward from said two vertical sections andbeing parallel to said top section, said bottom sections supporting saidwalking beam and being spaced from said top section to fit forward tothe next pair of slots 66. The pins 62 and 64 about said walking beam toprevent tipping thereof.

4. The device of claim 3, wherein said support means is made from onesheet of material.

5. The device of claim 1 wherein said support means provides for freemovement of said locking means relative to said support means when saidlocking means engages said rails.

6. The device of claim 1 wherein said actuating means includes aslidable coupling enabling said actuating means to accommodate relativemovement of said walking beam and said chassis.

7. The device of claim 1 wherein said actuating means includes a rodpivotally mounted to said chassis;

control means linked to said rod for selectively pivoting said rod intoa plurality of positions; and

means slidably engaging said rod, said engaging means being operablymounted on said walking beam to operate said locking means.

8. The device of claim 1 wherein said actuating means includes a rodpivotally mounted to said chassis, said rod having a non-circular crosssection;

I control means linked to said rod for selectively pivoting said rodinto a piurality of positions, said control means being operably mountedto move with said chassis; and

means slidably engaging said rod, said engaging means being operablymounted on said walking beam to operate said locking means and beingconstrained to pivot with said rod.

9. A horizontal earth boring device comprising an earth boring machine;

two rails supporting said earth boring machine;

a walking beam mounted under said earth boring machine; l

at least one hydraulic cylinder for driving said walking beam relativeto said earth boring machine, said cylinder being mounted at a first endto said walking beam and at a second end to said earth boring machine;

locking means operably mounted on said walking beam for selectivelyengaging said rails;

actuating means operably linked to said locking means for actuating saidlocking means, said actuating means including a rod having anon-circular cross section and being pivotally mounted to said earthboring machine, control means mounted on said earth boring machine andbeing linked to said rod for selectively pivotting said rod into aplurality of positions, and means slidably engaging said rod and beingconstrained to'rotate therewith, said engaging means being operablymounted on said walking beam to operate said locking means; and

section supporting said walking beam.

1. A horizontal earth boring device comprising an earth boring unit; a chassis for mounting said earth boring unit thereto; a plurality of rails supporting said chassis; a walking beam; drive means for driving said walking beam relative to said chassis; locking means operably mounted on said walking beam for selectively engaging said rails; actuating means operably linked to said locking means for actuating said locking means; and support means fixed to said chassis for slidably supporting said walking beam.
 2. The device of claim 1 wherein said walking beam is located under said chassis.
 3. The device of claim 1 wherein said support means includes a top section mounted to said chassis; two mutually parallel, vertical side sections, said vertical side sections being spaced to fit about said walking beam to keep said walking beam aligned; and two bottom sections extending inward from said two vertical sections and being parallel to said top section, said bottom sections supporting said walking beam and being spaced from said top section to fit about said walking beam to prevent tipping thereof.
 4. The device of claim 3, wherein said support means is made from one sheet of material.
 5. The device of claim 1 wherein said support means provides for free movement of said locking means relative to said support means when said locking means engages said rails.
 6. The device of claim 1 wherein said actuating means includes a slidable coupling enabling said actuating means to accommodate relative movement of said walking beam and said chassis.
 7. The device of claim 1 wherein said actuating means includes a rod pivotally mounted to said chassis; control means linked to said rod for selectively pivoting said rod into a plurality of positions; and means slidably engaging said rod, said engaging means being operably mounted on said walking beam to operate said locking means.
 8. The device of claim 1 wherein said actuating means includes a rod pivotally mounted to said chassis, said rod having a non-circular cross section; control means linked to said rod for selectively pivoting said rod into a plurality of positions, said control means being operably mounted to move with said chassis; and means slidably engaging said rod, said engaging means being operably mounted on said walking beam to operate said locking means and being constrained to pivot with said rod.
 9. A horizontal earth boring device comprising an earth boring machine; two rails supporting said earth boring machine; a walking beam mounted under said earth boring machine; at least one hydraulic cylinder for driving said walking beam relative to said earth boring machine, said cylinder being mounted at a first end to said walking beam and at a second end to said earth boring machine; locking means operably mounted on said walking beam for selectively engaging said rails; actuating means operably linked to said locking means for actuating said locking means, said actuating means including a rod having a non-circular cross section and being pivotally mounted to said earth boring machine, control means mounted on said earth boring machine and being linked to said rod for selectively pivotting said rod into a plurality of positions, and means slidably engaging said rod and being constrained to rotate therewith, said engaging means being operably mounted on said walking beam to operate said locking means; and support means fixed to said earth boring machine for slidably supporting said walking beam, said support means including a support structure having a top section mounted to said earth boring machine, two mutually parallel, vertical side sections having a slot therethrough to permit passage of said locking means relative to said support means, and two bottom sections extending inward from said two vertical sections parallel to said top section, said bottom section supporting said walking beam. 